Many types of batteries and other power cells are known, based upon a relatively wide range of electrical couples, and among the most popular electrical couples are those containing zinc.
For example, zinc is frequently employed in primary batteries. Such batteries are typically found in many simple flashlight batteries to provide a relatively inexpensive and reliable power source. Although manufacture of Zn/C batteries is typically simple and poses only relatively little environmental impact, various disadvantages of Zn/C batteries exist. Among other things, the ratio of power to weight in commonly used Zn/C batteries is relatively poor.
To improve the power to weight ratio, alternative coupling partners for zinc may be utilized. Among other metal oxides, mercury oxide or silver oxide have been employed to manufacture primary batteries with significantly improved power to weight ratio. However, the toxicity of mercury oxide is frequently problematic in manufacture, and tends to become even more problematic when such batteries are discarded. On the other hand, silver oxide as a coupling partner for zinc is environmentally substantially neutral. However, silver oxide is in many instances economically prohibitive, especially where such batteries are used in everyday devices (e.g., portable CD player or radio).
Alternatively, zinc air battery systems may be employed in applications where a favorable ratio of weight to capacity is particularly important. In such zinc air batteries, atmospheric oxygen is used as a gaseous coupling partner for zinc, which is typically provided in form of gelled zinc powder anodes. Among the various advantages in such batteries, using air (i.e., oxygen) as coupling partner for zinc significantly reduces weight. However, reasonable shelf life of such batteries can often only be achieved by using an airtight seal. Furthermore, to provide continuous operation, air must have an unobstructed path through the battery to the cathode so that the oxygen in the air is available to discharge the cathode. Moreover, commercial applications of zinc-air batteries have previously been limited to primary or non-rechargeable types.
Thus, while zinc may be combined with various redox partner to provide at least a somewhat advantageous power to weight ratio, many of those redox couples limit use of such batteries to primary, non-rechargeable batteries. Consequently, considerable effort has been made to form a redox pair in which zinc can be used in a secondary, rechargeable battery.
For example, zinc may form a redox pair with nickel to provide a rechargeable redox system. While many rechargeable zinc/nickel batteries frequently exhibit a relatively good power to weight ratio, several problems of the zinc/nickel redox pair persist. Among other difficulties, such batteries tend to have a comparably poor cycle life of the zinc electrode. Moreover, nickel is known to be a carcinogen in water-soluble form, and is thus problematic in production and disposal.
To circumvent at least some of the problems with toxicity, zinc may be combined with silver oxide to form a secondary battery. Rechargeable zinc/silver batteries often have a relatively high energy and power density. Moreover, such batteries typically operate efficiently at extremely high discharge rates and generally have a relatively long dry shelf life. However, the comparably high cost of the silver electrode generally limits the use of zinc/silver batteries to applications where high energy density is a prime requisite.
In a further, relatively common secondary battery, zinc is replaced by cadmium and forms a redox couple with nickel. Such nickel/cadmium batteries are typically inexpensive to manufacture, exhibit a relatively good power to weight ratio, and require no further maintenance other than recharging. However, cadmium is a known toxic element, and thereby further increases the problems associated with health and environmental hazards.
Thus, despite the relatively widespread use of secondary batteries, numerous problems persist. Among other things, all or almost all of the known secondary batteries can only be continuously operated under conditions in which the cathode compartment is separated from the anode compartment by a separator. Loss of the separation (e.g., due to puncture of the membrane by dendrites forming during recharge) will typically result in undesired plating of one or more components of the electrolyte on the battery electrode and thereby dramatically decrease the performance of such batteries.
Although numerous secondary batteries are known in the art, all or almost all of them suffer from one or more disadvantages. Particularly, the performance of known secondary batteries will significantly decrease when anolyte and catholyte of such batteries will inadvertently mix. Therefore, there is still a need to provide improved batteries.